Ion channels are proteins that span the lipid bilayer of the cell membrane and provide an aqueous pathway through which specific ions such as Na+, K+, Ca2+ and Cl− can pass (Hille et al., 1999). Potassium channels represent the largest and most diverse sub-group of ion channels and they play a central role in regulating the membrane potential, cell volume, signal transduction controlling cellular excitability (Armstrong & Hille, 1998). Potassium channels have been categorized into gene families based on their amino acid sequence and their biophysical properties (for nomenclature see (Gutman et al., 2003) and http://www.iuphar-db.org/DATABASE/ReceptorFamiliesForward?type=IC).
Compounds which modulate potassium channels have multiple therapeutic applications in a number of areas/disorders including cardiovascular, neuronal, renal, metabolic, endocrine, auditory, pain, respiratory, immunological, inflammation, gastrointestinal, reproduction, cancer and cell proliferation, (for reviews see (Ehrlich, 2008; Wulff & Zhorov, 2008; Kobayashi & Ikeda, 2006; Mathie & Veale, 2007; Wulff et al., 2009; Camerino et al., 2008; Shieh et al., 2000; Ford et al., 2002; Geibel, 2005). More specifically potassium channels such as those formed by Kir3.x, Kv4.x, Kir2.x, Kir6.x, Kv11.x, Kv7.x, KCa, K2P, and Kv1.x along with their ancillary subunit are involved in the repolarisation phase of the action potential in cardiac myocytes (Tamargo et al., 2004). These potassium channels subtypes have been associated with cardiovascular diseases and disorders including atrial arrhythmias, ventricular arrhythmias, cardiomyopathy, hypertrophy long QT syndrome, short QT syndrome, Brugada syndrome; and all of which can cause cardiac failure and fatality (Marban, 2002;Novelli et al., 2010; Tamargo et al., 2004).
Inwardly rectifying potassium channels are members of a large superfamily comprised of Kir1.x to Kir7.x. The Kir3.x subfamily are G-protein coupled inwardly rectifying potassium ion channels comprised of 4 mammalian subunit members Kir3.1 to Kir3.4. These subunits form homo- or hetero-tetrameric ion channels involved in potassium flux across the membrane. Kir3.x ion channels are expressed in the cardiovascular system (Kir3.1 and Kir3.4), central nervous system (Kir3.1, Kir3.2, Kir3.3>Kir3.4), gastrointestinal tract (Kir3.1 and Kir3.2) and have been implicated in a number of disease areas including cardiac arrhythmias, pain, Parkinson's disease, Down's Syndrome, epilepsy/seizure, addiction, depression and ataxia (Luscher & Slesinger, 2010; Tamargo et al., 2004) The human G-protein coupled inwardly-rectifying potassium channel subunits Kir3.1 and Kir3.4 are predominantly expressed in the supraventricular regions (including atria, nodal tissue, pulmonary sleeve) and conduction system of the heart and are believed to offer therapeutic opportunities for the management of atrial fibrillation for several different reasons (see review of (Ehrlich, 2008):    (1) Kir3.1/3.4 underlies IKACh: There is evidence that a tetrameric assembly of Kir3.1 and/or Kir3.4 subunits underlies the cardiac acetylcholine/adenosine activated inwardly-rectifying potassium current (hereto referred to as IKACh) in the heart due to similar biophysical (Krapivinsky et al., 1995; Duprat et al., 1995; Corey & CLAPHAM, 1998; Corey et al., 1998) and pharmacological (Jin & Lu, 1998; Jin et al., 1999; Jin & Lu, 1999; Drici et al., 2000; Cha et al., 2006; Dobrev et al., 2005; Voigt et al., 2010b) properties (for review see (Hibino et al., 2010; Belardinelli et al., 1995)).    (2) IKACh is involved in AF: The Kir3.1 subunit cannot form a functional homotetramer or cannot traffic to the membrane (Philipson et al., 1995; Hedin et al., 1996; Woodward et al., 1997) and as such genetic knockout of Kir3.4 gene in the mouse results in the lack of a functional IKACh in the atria (Wickman et al., 1998). This genetic ablation of IKACh results in resistance to atrial fibrillation (Kovoor et al., 2001). These data support the notion of an assembly of Kir3.1/3.4 and the importance of IKACh in the initiation and sustaining of AF. Furthermore, single nucleotide polymorphisms of Kir3.4 gene have been correlated with paroxysmal lone AF in a Chinese population (Zhang et al., 2009). However, no function has been ascribed to these polymorphisms.    (3) IKACh is an atrial-specific target: High levels of Kir3.1 and Kir3.4 gene expression (Gaborit et al., 2007b) and large IKACh are found in both the left and right human atria (Dobrev et al., 2001; Dobrev et al., 2005; Voigt et al., 2010b; Wettwer et al., 2004; Bosch et al., 1999; Voigt et al., 2010a). This contrasts with the human ventricle, where mRNA (Gaborit et al., 2007b) and current expression are considerable smaller, and the number of cells expressing IKACh and the ACh sensitivity is small compared to the atria (Koumi & Wasserstrom, 1994; Koumi et al., 1994). In conjunction with a lower density of parasympathetic innervations (Kent et al., 1974), this argues against a functional role of IKACh in human ventricles (Brodde & Michel, 1999; Belardinelli et al., 1995). This is further supported by the lack of effect of selective IKACh inhibitors on ventricular repolarisation in in vitro (Cha et al., 2006) and in vivo dog studies (Hashimoto et al., 2006; Hashimoto et al., 2008; Machida et al., 2011). The predominant expression of IKACh in the atria cf. the ventricle provides a mechanism to modulate atrial repolarisation without interfering with ventricular repolarisation and potentially inducing fatal ventricular arrhythmia (Hashimoto et al., 2006).    (4) Constitutive-activation of IKACh in chronic AF: The carbachol-induced IKACh recorded from atrial myocytes from patients with chronic AF is smaller than those from patients in sinus rhythm, a phenomenon initially thought to be due to decreased Kir3.4 mRNA and protein levels (Bosch et al., 1999; Brundel et al., 2001a; Brundel et al., 2001b; Dobrev et al., 2001). However, it was later demonstrated that the blunted response to carbachol is due to IKACh being constitutively active in the absence of agonist (Dobrev et al., 2005). Similar observations have also been reported in the atria and pulmonary vein in the tachypaced-dog model of AF (Cha et al., 2006; Ehrlich et al., 2004; Voigt et al., 2008; Makary et al., 2011). Ionic remodeling (for review see (Schotten et al., 2011; Workman et al., 2008), including the constitutive-activation of IKACh, contributes to the shortening of action potential duration observed in chronic AF human patients (Dobrev et al., 2001; Dobrev et al., 2005; Bosch et al., 1999; Wettwer et al., 2004) and tachypaced dog atrial myocytes (Ehrlich et al., 2004; Ehrlich et al., 2007; Cha et al., 2006), which, in turn, causes a reduction in the atrial effective refractory period (Brundel et al., 2002b; Brundel et al., 2002a; Workman et al., 2008) predisposing to the generation of arrhythmias. In addition, the heterogeneous distribution (Gaborit et al., 2007a; Lomax et al., 2003; Sarmast et al., 2003; Voigt et al., 2010b) of constitutively active IKACh (Dobrev et al., 2005; Cha et al., 2006; Ehrlich et al., 2004) across the atria is expected to increase the dispersion of atrial repolarization/refractoriness (Liu & Nattel, 1997; Kabell et al., 1994; Schauerte et al., 2000; Chiou et al., 1997) and in turn increase vulnerability to transient atrial arrhythmias (Liu & Nattel, 1997; Kabell et al., 1994). Pharmacological studies have shown that selective inhibition of IKACh has as a more pronounced prolonging effect on action potential duration in the remodeled dog atria (Cha et al., 2006; Ehrlich et al., 2007). Prolonging the action potential duration by inhibiting IKACh or the constitutive IKACh could present safer pharmacological interventions for protecting against atrial arrhythmias such as chronic atrial fibrillation and atrial flutter compared to traditional class III antiarrhythmics by prolonging the atrial refractory period while leaving ventricular refractoriness unaltered (Cha et al., 2006; Tanaka & Hashimoto, 2007; Hashimoto et al., 2007; Machida et al., 2011).    (5) IKACh Inhibitors in AF: Class III antiarrhythmics have been widely reported as a preferred method for treating cardiac arrhythmias (Colatsky et al., 1990). Traditional and novel class III antiarrhythmic potassium channel blockers have been reported to have a mechanism of action that includes the direct modulation of Kir3.1/3.4 or IKACh. The known antiarrhythmics dronedarone (Altomare et al., 2000; Guillemare et al., 2000), amiodarone (Watanabe et al., 1996; Guillemare et al., 2000), propafenone (Voigt et al., 2010a) and flecamide (Voigt et al., 2010a), ibutilide (Borchard et al., 2005) quinidine (Kurachi et al., 1987; Hara & Kizaki, 2002), verapamil (Hibino et al., 2010), AVE0118 (Gögelein et al., 2004; Voigt et al., 2010a) NIP-142 (Matsuda et al., 2006; Hashimoto et al., 2007; Tanaka & Hashimoto, 2007), NIP-151 (Hashimoto et al., 2008), NTC-801 (Machida et al., 2011) have all been reported as potassium channel blockers of Kir3.1/3.4 or IKACh in atrial myocytes. A benzopyran derivative, NIP-142, preferentially blocks Kir3.1/3.4 with selectivity over other cardiac channels, prolongs the atrial refractory period and terminates atrial fibrillation and flutter in in vivo canine models (Nagasawa et al., 2002; Tanaka & Hashimoto, 2007). From the same chemical class, both NIP-151 and NTC-801 are highly selective IKACh inhibitors and have been shown to be effective in terminating AF in the vagal-induced and aconitine-induced canine models of AF (Hashimoto et al., 2008; Machida et al., 2011). The latter, NTC-801, has also been shown to prevent the induction of AF in an atrial-tachypacing dog model of persistent AF (AT-AF) (Machida et al., 2011) in which the atria exhibit electrical remodeling akin to chronic AF in man (Cha et al., 2006; Ehrlich et al., 2004; Voigt et al., 2008; Makary et al., 2011). The selective IKACh inhibitor peptide tertiapin (Jin & Lu, 1998; Drici et al., 2000) has also been shown to be effective in terminating AF in both vagal-induced and acontine-induced canine models of AF (Hashimoto et al., 2006). None of the agents were shown to affect ventricular repolarisation (QTc or VERP) at therapeutically relevant doses. These data support the utility of IKACh inhibitors for the cardioversion and prevention of recurrence of supraventricular arrhythmias such as AF and atrial flutter without effecting ventricular function. A combination of anti-arrhythmics with other ion channel modulating drugs may also provide greater (synergistic) benefit in the treatment of atrial arrhythmias as shown for the non-selective anti-arrhythmics drugs amiodarone/dronedarone and ranolozine (Burashnikov et al., 2010; Sicouri et al., 2009) and the combination of the IKr inhibitor sotalol with an IKur inhibitor BMS-394136 (Sun et al., 2010). As such, the combination of a selective IKACh inhibitor with other ion channel or ion exchanger modulating drugs could provide added clinical benefit.    (6) IKACh inhibition in stroke prevention in AF: Atrial fibrillation is associated with a 5-fold increased risk for stroke and in the United States approximately 15% to 25% of all strokes can be attributed to AF (Steinberg, 2004). Regardless of the approach to arrhythmias treatment (rate, rhythm, ablation), the prevention of thromboembolism is a cornerstone of clinical treatment of atrial arrhythmias. Constitutive activation of IKACh has been reported to contribute to the contractile deficit associated with AF in the tachypaced-atrial dog model of AF. Inhibition of IKACh could be a novel target to prevent hypocontractility-related thrombo-embolic complications (Koo et al., 2010). IKACh inhibitors alone or in combination with other anti-platelet or anti-coagulant therapies may significant reduce the risk of stroke and thromboembolism in AF.    (7) Role of autonomic system in AF: Clinical (Coumel, 1994; Coumel, 1996; Pappone et al., 2004; Tan et al., 2006; Yamashita et al., 1997; Huang et al., 1998) and experimental (Liu & Nattel, 1997; Ogawa et al., 2007; Sharifov et al., 2004; Jayachandran et al., 2000; Scherlag et al., 2005; Horikawa-Tanami et al., 2007; Po et al., 2006) observations highlight the importance of the autonomic nervous system and in particular parasymthpathetic/vagal activation in AF. The electrophysiologic substrate of AF is often latent until vagal activation which is sufficient to induce and maintain AF via IKACh activation. IKACh inhibitors are expected to be effective in the treatment of paroxysmal AF with a neurogenic (vagal) component.    (8) Autonomic system in the initiation of AF: Ectopic activity arising from the pulmonary veins and sleeves (PV) has been shown to play a prominent role in the initiation and maintenance of AF (Haissaguerre et al., 1998; Pappone et al., 2000). Pulmonary vein isolation is a procedure used frequently to eliminate the triggers arising from the pulmonary veins. Electrical activity, originating from PV sleeves following parasympathetic and/or sympathetic stimulation, has been proposed as a potential trigger in the initiation of AF (Burashnikov & Antzelevitch, 2006; Patterson et al., 2005; Patterson et al., 2006; Wongcharoen et al., 2007; Lo et al., 2007). Studies in animal models have shown an increase in the time-dependent IKACh in the pulmonary sleeve of the AT-AF dog (Ehrlich et al., 2004). Autonomic nerve stimulation reduces PV-sleeve action potential duration and causes triggered PV firing that is suppressed by muscarinic cholinergic receptor blockade (Patterson et al., 2005). Fibrillatory cycle length shortening in response to vagal stimulation points to ACh effects on PV drivers (Takahashi et al., 2006). Thus, inhibition of IKACH could remove vagally enhanced PV drivers that initiate and maintain AF.    (9) Autonomic nervous system in atrial remodeling: Auto-antibodies to the muscarinic M2 receptor have been shown to increase expression of Kir3.1 and Kir3.4 mRNA and Kir3.4 protein in the rabbit heart, resulting in both electrical and structural remodeling creating a substrate for AF (Hong et al., 2009). Increased vagal-nerve activity has been shown to promote atrial electrical remodeling in atrial tachypaced dogs; this effect was partially revered by atropine and fully reversed by a combination of cholinergic block and a vasoactive intestinal polypeptide (VIP) antagonist (Yang et al., 2011). Clinical studies have also shown that parasympathetic block may promote the recovery from AERP shortening associated with rapid atrial pacing (Miyauchi et al., 2004). Although the mechanism that underlies these observations is not fully elucidated, inhibition of IKACH alone or in combination with other agents could prevent or reverse atrial remodeling associated with AF.Beyond use in the treatment of atrial arrhythmias, Kir3.1/3.4 inhibitors may have utility in a number of other indications:    (1) IKACh and sinoatrial and atrioventricular node function: Acetylcholine (ACh) is an important neuromodulator of cardiac function that is released upon stimulation of the vagus nerve. Negative chronotropic and dromotropic effects are cardiovascular features associated with ACh release upon parasympathetic stimulation. In the mammalian heart, cholinergic parasympathetic fibres are extensively distributed to the sinus node, to the atria and to the atrioventricular (AV) node. Vagal stimulation produces a negative chronotropic and dromotropic effect on the heart and can induce or predispose to atrial arrhythmias due to shortening of the atrial ERP. Vagal stimulation increases AV-ERP (ALANIS et al., 1958; ALANIS et al., 1959), prolongs atrial conduction time (Martin, 1977) and produces a negative dromotropic effect. Selective inhibition of IKACh with tertiapin has been shown to inhibit the dromotropic and blunts the chronotropic effects of ACh on the heart and relieve AV block (Drici et al., 2000). The abundance of Kir3.1 and Kir3.4, is reported to be equal in the sinus node and atrial muscle (Tellez et al., 2006). Activation of IKACh causes decreased spontaneous activity, hyperpolarization of the maximum diastolic potential, and a decrease in the diastolic depolarization rate of the SA node contributing to the negative chronotropic effect of ACh (Dobrzynski et al., 2007; Han & Bolter, 2011; Rodriguez-Martinez et al., 2011). Atrial fibrillation is associated with structure and ionic remodelling in the atria (for review see (Schotten et al., 2011; Workman et al., 2008) and damage to the SAN (Thery et al., 1977). Clinical studies have shown that sick sinus syndrome is frequently associated with AF and atrial flutter (Ferrer, 1968; Gomes et al., 1981). Sinoatrial node dysfunction is a heterogeneous disorder of unknown etiology characterized by a variety of supraventricular arrhythmias with symptoms of persistent bradycardia, tachycardia, syncope, palpitations, and dizziness. The mechanism underlying the abnormal rhythm is incompletely understood. However, atropine, a muscarinic antagonist, is used in the treatment of sick sinus syndrome. However, side-effects preclude its long term use (1973). Taken together, these data highlight both the presence and functional importance of IKACh in the SAN and AVN and indicate the potential of an IKACh inhibitor to modulate AV conduction in setting of hypervagotony or early inferior myocardial infarctions (Drici et al., 2000) and provide a novel mechanism in the treatment of sinus node dysfunction.    (2) Kir3.1/3.4 inhibitors and prevention of thromboembolism: Current approaches to the prevention of thromboembolism include the use of anti-platelet therapy (e.g. aspirin) or anticoagulation therapy including the use vitamin K antagonist warfarin, and oral agents, including direct thrombin inhibitors such as dabigatran, ximelagatran and factor Xa inhibitors such as apixaban, rivaroxaban, and edoxaban, betrixaban and YM150 (for review see (Ezekowitz et al., 2010)). Damaged blood vessels, red blood cells and platelets release ADP and induce platelet aggregation. Pathological thrombosis formation can lead to vascular occlusion, resulting in ischemic insults. The platelet ADP receptor designated P2Y12, the target of the antithrombotic agents like clopidogrel, activates Kir3.x channels via Gi/o proteins (Hollopeter et al., 2001). Human platelets have been shown to express both Kir3.1 and Kir3.4 protein by Western blot (Shankar et al., 2004). Kir3.1/3.4 inhibitors, such as SCH23390 and ethosuximide, can inhibit ADP- and thrombin-mediated platelet aggregation (Shankar et al., 2004; Kobayashi et al., 2009). Therefore, Kir3.1/3.4 inhibitors may be effective for preventing thrombosis and thromboembolic diseases including stroke, myocardial infarction and peripheral vascular diseases (Kobayashi & Ikeda, 2006).    (3) Kir3.4 and pancreatic function: Although predominantly expressed in the heart Kir3.4 has been cloned from the human pancreas (Chan et al., 1996) and has been detected in α, β, δ cells of the mouse pancreas (Yoshimoto et al., 1999; Ferrer et al., 1995; Iwanir & Reuveny, 2008). Electrophysiological studies have shown that somatostatin and α2-adrenoceptor agonists activate sulfonylurea-insensitive K30 channels by a G protein-dependent mechanisms, and thereby inhibit activity of Kir3.4-expressing β-cells (Rorsman et al., 1991), (Yoshimoto et al., 1999), suggesting that activation of Kir3 channels may inhibit insulin secretion. Additionally, somatostatin released from 6 cells activates Kir3 channels in glucagon-expressing α cells (Yoshimoto et al., 1999). The adrenaline-induced hyperpolarisation of mouse pancreatic cells has been shown to be a tertiapin-sensitive inwardly-rectifying potassium current (Iwanir & Reuveny, 2008). Therefore, pancreatic Kir3.4 channels may be related to control of pancreatic hormone secretion and have utility in the treatment of diabetes mellitus alone or in combination with sulfonylureas and other oral agents (Kobayashi & Ikeda, 2006).    (4) Kir3.1/3.4 in the central nervous system: In addition to expression in the heart, Kir3.1 and Kir3.4 mRNA have been detected in the parts of the brain (Wickman et al., 2000; Mark & Herlitze, 2000; Hibino et al., 2010). A number of psychotropic and antidepressant drugs have been shown to inhibit the Kir3.1/3.4 channels including paroxetine (Kobayashi et al., 2006), fluoxetine (Kobayashi et al., 2003), reboxetine (Kobayashi et al., 2010), atomoxetine (Kobayashi et al., 2010), mipramine, desipramine, amitriptyline, nortriptyline, clomipramine, maprotiline, citalopram (Kobayashi et al., 2004), and ethosuximide (Kobayashi et al., 2009). This suggests that the Kir3.x inhibition may underlie some of the therapeutic effects related to the CNS. As such, Kir3.1/3.4 inhibits may have utility in the treatment of neurological and neuropsychiatric disorders diseases including pain, depression, anxiety, attention-deficit/hyperactivity disorder, and epilepsy.    (5) Kir3.1/3.4 and pituitary function: Kir3.1 and Kir3.4 have been detected in the pituitary cells of the rat (Gregerson et al., 2001; Wulfsen et al., 2000) where they potentially play a critical role in excitation-secretion coupling. As such, Kir3.1/3.4 inhibitors could be used to modulate neuro-endocrine function and the secretion of pituitary hormones. However, corroborative data in man is currently lacking.    (6) Kir3.1/3.4 and cancer: In addition, other reports have cloned Kir3.1 and Kir3.4 from human breast cancer cell line (Wagner et al., 2010) and suggest they may be involved in cellular signaling and cancer (Dhar & Plummer, III, 2006; Plummer, III et al., 2004). Although additional data are required to establish a causal link, targeting Kir3.1/3.4 could be useful in the treatment of breast cancer.
Nissan Chemical Industries have reported a series of substituted benzopyrans as atrial-specific antiarrythmics.
In WO 01/21610 Nissan discloses a series of benzopyran derivatives which are claimed to increase the functional refractory period in an ex vivo preparation of guinea pig atrial tissue with potential use as atrial-specific antiarrythmics.
In WO 02/064581, WO 03/000675 and WO 2005/080368 Nissan discloses a series of 4-amino substituted benzopyran derivatives which are claimed to selectively prolong the atrial refractory period in an in vivo dog model of vagal-induced atrial fibrillation with potential use as atrial-specific antiarrythmics.
In WO 2008/0004262 Nissan discloses a series of fused tricyclic benzopyran derivatives which are claimed to selectively prolong the atrial refractory period in an in vivo dog model of vagal-induced atrial fibrillation with potential use as atrial-specific antiarrythmics.
The above Nissan patents do not specify a biological target, but in subsequent publications (Hashimoto et al, 2008) compounds of these documents have been disclosed as blockers of the Kir3.1/3.4 channel and the IKACh cardiac current.
WO 2010/0331271 discloses a series of derivatives of the flavone acacetin which are claimed inter alia as blockers of the cardiac acetylcholine-activated current (IKACh) with potential use as atrial-specific antiarrythmics.
In WO 2009/104819 Otsuka Pharmaceuticals discloses a series of benzodiazepine derivatives which are claimed as blockers of the Kir3.1/3.4 channel with potential use as atrial-specific antiarrythmics.
Thienopyrimidines, furanopyrimidines and thienopyridines have been shown to modulate ligand-gated and voltage-gated ion channels as well as GPCRs.
US2005/0222175 and US2005/022176 disclose 4-piperidylamino substituted thieno[2,3-d]pyrimidines which modulate the 5-HT receptor, in particular, the 5-HT2b receptor for the treatment of pulmonary arterial hypertension, heart failure, and hypertension.
US2007/0287717 (Vertex) discloses 2-phenyl substituted thieno[2,3-d]pyrimidines which modulate voltage-gated sodium and calcium channels for the treatment of various disorders including epilepsy and neuropathic pain.
US2009/0270405 and WO2011/053292 disclose quinuclidine substituted thieno[2,3-d]pyrimidines which modulate the alpha-2-nicotinic acetylcholine receptor for the treatment of affective and neurodegenerative disorders.
WO2004/11057 (Xention) discloses 4-alkylamino and 4-alkoxy thieno[2,3-d]pyrimidines as blockers of the Kv1.5 voltage-gated potassium channel for the treatment of Atrial Fibrillation.
WO2005/121149 (Xention) discloses furano[2,3-d]pyrimidines as blockers of the Kv1.5 voltage-gated potassium channel for the treatment of Atrial Fibrillation.
WO2007/066127 (Xention) discloses 4-aminoalkyl and 4-alkoxy substituted thieno[3,2-c]pyridines as blockers of the Kv1.5 voltage-gated potassium channel for the treatment of Atrial Fibrillation and also as blockers of the Kv1.3 voltage-gated potassium channel for the treatment of autoimmune disorders.
WO2006/061642 (Xention) discloses 4-alkylamino substituted thieno[2,3-b]pyridines as blockers of the Kv1.5 voltage-gated potassium channel for the treatment of Atrial Fibrillation and also as blockers of the Kv1.3 voltage-gated potassium channel for the treatment of autoimmune disorders.
Ramakrishna et al disclose fused thieno[2,3-d]pyrimidines and 4-alkoxythineo[2,3-d]pyrimidines which act as antagonists of the 5-HT6 receptor.
Modica et al (2004) disclose 4-piperazinyl thieno[2,3-d]pyrimidines which behave as competitive antagonists of the 5-HT3 receptor.
Thienopyrimidines have also been shown to be useful against other biological targets. US2003/0153556 discloses 4-piperazinyl and 4-homopiperazinyl substituted thieno[2,3-d]pyrimidines for the treatment of thrombosis.
WO2006/079916, WO2006/103555, WO2006/103545, WO2006/103544, and WO2006/100591 (Pharmacia and Upjohn) discose 2-amino-4-piperidyl substituted thieno[2,3-d]pyrimidines for the inhibition of ADP-mediated platelet aggregation.
US2011/0166121 (LG Lifesciences) discloses fused 4-piperidinyl and 4-piperazinyl thieno[2,3-d]pyrimidines for the inhibition of platelet aggregation.
WO2011/029054 (University of Michigan) discloses 4-piperazinyl and 4-homopiperazinyl theino[2,3-d]pyrimidines which inhibit the interaction of menin with the proto-oncogene Mixed Lineage Leukemia (MLL).
WO2004/014850 (Predix Pharmaceuticals) discloses 4-(aminopiperidyl) substituted thieno[2,3-d]pyrimidines as Neurokinin antagonists.
WO2004/065391 (Almirall Prodespharma) discloses 4-amino-6-carbonitrile substituted thieno[2,3-d]pyrimidines as inhibitors of PDE7 for the treatment of T-cell mediated immune disorders.
WO2006/030031 (Janssen/Addex) discloses 4-alkylamino substituted thieno[2,3-d]pyrimidines as positive allosteric modulators of the mGluR2 receptor.
WO2006/071988 (Memory Pharmaceuticals) discloses 4-alkoxy, 4-alkyl, and 4-aminoalkyl thieno[2,3-d]pyrimidines as inhibitors of PDE 10.
WO2009/007115 (Syngenta) discloses 4-tropanyl substituted thieno[2,3-d]pyrimidines that are claimed to have usefulness as pesticides.
Gorja et al (2011) disclose 4-alkynyl substituted tricyclic thieno[2,3-d]pyrimidines which were tested for cytotoxic activity against the chronic myelogenous leukemia (CML) cell line.
Jang et al (2010) disclose a series of 4-N-piperazinyl thieno[2,3-d]pyrimidines which were tested for immunosuppressive activity in a mixed lymphocyte reaction (MLR) assay.
Tasler et al (2010) disclose a series of 4-(4-aminopiperidyl) substituted thieno[2,3-d]pyrimidines which act as agonists for the 33-adrenoreceptor.